As a new nondestructive testing method, the accurate measurement of laser ultrasonic velocity is of great significance for judging the internal crack defects of composites, calculating the elastic modulus, residual stress and grain size. Based on the finite element analysis method, the thermoelastic effect of laser induced ultrasonic vibration, the time-of-flight method and laser grating method for measuring ultrasonic velocity are studied in this paper. Firstly, the waveforms of laser point source, line source and laser grating are compared and analyzed. Secondly, the error analysis of the wave velocity under different radius laser point source, different half width laser line source and different grating spacing is carried out. The simulation results show that the laser grating method has higher stability and smaller measurement error. In addition, this method is less affected by other waves and the external environment. This paper provides a basis for improving the measurement accuracy of laser ultrasonic velocity and further applying laser ultrasonic velocity to nondestructive testing and measurement of related physical quantities.